Electrically-heated device and method of manufacture thereof



Ffa.A 15A, 1927.y 1,617,489

E. N. LIGHTFOOT ELEGTRICALLY HEATE'D DEVICE AND METHOD-0F MANUFAGTURE'rasnso Filed June 2. 1922 INVENTOR.

l 50 the relative temperatures of the parts being Patented Feb. 19,27.-

UNITED STATES PATENT" orfricia;

EDWIN N. LIGHVTFOOT, l' NEW YORK, N. Y., AISSIGNOB TO CUTLEB-HAMHER MFG.C0., 0F MILWAUKEE, WISCONSIN, A, COBBORTlON 0F WISCONSIN.- y

ELECTBICALLY-IIEATED DEVICE A ND Aspiration ined :une 2,

This invention relates toelectrically heated devices and va method ofmanufacture thereof.

In' practice thereare instances where it is desired to electrically heatelements which areA available as standard articles of manu facture, orwhich by reason of the material employed therefor or Athc requiredaccuracy of construction thereof or for other reasons are-preferably lifnot necessaily formed separately from the completed devices in whichthey are incorporated. However, asis well known, it has been foundexceedingly difiicult to mechanically combine such separately formedelements with their heating elements in an eicient thermal relation, andthe present invention hasv among its objects to overcome suchdifficulties. More specifically the invention has ampng its objects toprovide an integral electrically heated device comprising separatelyformed heated and heating elements so united as to provide a strongpermanent bond therebetween by virtue of which said elements are insuredan excellent thermal relationship Another object is to provide a methoof manufacture wherebysuch a device may be readily formed withoutrequiring contact between 4the heating and heated elements thereof toobtain the desired transfer of heat therebetween, but enabling theheating element or elements to be placed in direct contact with theheated element for conven-v ience in manufactureifA desired.

, Another object is to provide a method of manufacture applicable ,tovarious types of heated and heating .elements of Astandard and specialconstruction.`

Various other objects 'and advantages of 40 vthe invention willhereinafter appear.

Accordingto thepresent invention it is proposed to place the heatedelement and its heating elementorelements after tem-` porary seculementthereof ,inthe desired relation-within la mold and "then pour moltenlmetal into lthe mold to form a cast band about the heated and- `heatingelements to mechanically bond the same and to exert thereon acompression force upon cooling,

controlled if desired-to regulate such com-` pression force.

^' Certain embodlments of the invention are illustrated in, thel accomanying drawing u and the seme will now be ascribed.' it being )marronesIANUIACTUBE '.rmsnnor.

1922. semi No. 565330;

understood that the invention is susceptible of embodiment in otherforms' without departing from the scope of the appended claims.

In' the drawing which is more or less diagrammatic,

Figures 1 and 2 show ed branding iron; l F ig. 3 shows an electricallyheated pipe section; and

Fig. 4v shows an e cible.

Referring tooFigs. 1 and'2 the branding iron comprises a cylindricalcore section: 1` to which is fixed a die 2 and aboutwhich. is coiled aheating element 3. The heating element 3 which may be of any suitabletype but preferably of thetype disclosed in my Patent No. 1,359,400,anted November 16, 1920, is enclosedin a metal shell 4 cast onto andsurrounding the core 1, said heating element having terminals 5extending through the shell. 'The type of heating element specificallyaforemention d comprises. a helical resistor enclosed in a t bular metal{'ackat' from which it is thoroughlyl insu- ,ate

The core 1 which is of any preferred metal and formed in any preferredmanner is initially wrapped with the heating'element 3, the latter beingpreferably although not necessarily in direct contact with the former.When so assembled the core and heating element are placed in a moldbeing retained inthe desired relation either by frictional engagementthereof or by temporary securing means after Vwhich molten iron, brass,bronze, aluminum or other prefer-red metal is poured into the mold toform the shell 4, such molten metal completelv surrounding the coils' ofthe heatmg e ement and contacting with the core. Thereupon the moltenmetal is allowed to cool wit consequent shrinkage or contraction w chcauses it to exert a compression 100 force upon the core 1.

Thus the shell is caused Vto tightly graspthe core to mechanicallysecure the former and the embedded heating element to th'e danelectrically heatlectrically heated crucore even assuming the latter tobe provided 15- with a fairly smooth surface. Also the in timete contactthus produced between the shell and core affords excellent heat con-jduction between the heating eleni'ent and cone the shell thus renderingconml l essary. As will be understood the core or heating element orboth may be heated durbeing `controlled as desired toregulate thecompression force of the shell on the core upon cooling. v

Referring to Fig. 3 the same shows a pipe section 6 having a similarheating element 7 coiled thereabout and encased in a similar shell 8cast onto and about the pipe section 6. .This device may -also be formedas above described. v 'p Referring to Fig. 4 the same shows a crucible 9to be formed of drawn steel or cast iron and to be supported in a casing10 from which the same is removable. The crucible which ordinarily mustbe formed with special care and 'hence formed separately .has a heatingelement 11 coiled about its cylindrical section. lIn this instance theheating elementA preferably ofthe type aforementioned is'reilexed andhas its reflexed portions bent to surround the crucible instead ofhaving each turn thereof completely surrounding the element to be heatedas in the devices y above described. However, as will be understood theheating element might be arranged on the crucible in the manner abovedescribed or in any other preferred manner whereby the same may beencased in a shell 16 cast onto and surrounding the cruci- I ble .A swinl be understood the Shen -16 muv be cast onto the crucible asabovedescribed` the heating element being retained on the crucible byany preferred means during the casting operation. l

In the manufacture of such crucibles it has been found that in someinstances the shirnkage of the shell is so great as to cause crackingthereof unless the crucibles are preheated, which may be readilyaccomplished by pouring molten metal into the crucibles.

-A convenient method is to use a sufficiently large ladle to supply ththe crucible and the mold, the crucible ing supplied before the metal ispoured into the mold. This raises the temperature of the crucible. wall-to a high degree but the maximum temperature thus obtained is lowerthan the temperature of the metal poured into the mold and lconsequentlythe shell will shrink more than the Crucible wall to exert a compressionforce upon the wall but to a degree insuiiicient to cause it to crack. Y

lVhat I claim as new and desire to secure by Letters Patent is:

1. An electrically, heated device compriscasting ofthe shell, thetemperatures ing an element to be heated, a heating element therefor anda cast metal shell containing said heating element and surrounding saidelement to be heated, said shell being contracted on the latter elementto permanently subject the same to a compression force.

2. An electrically heated device comprising an element to be heated, ametal shell cast around and contracted on said element for intimatecontact and lirm engagement therewith and a heating element for theformer element cast in said shell.

v3. An electrically heated device comprising an element to be heated, aheating elementk therefor having a metal jacket and a I metal shell castupon and surrounding both of said elements, said shell being contractedonv said elements to tightly bond the same in an eicient thermalrelationship.

4. An electrically heated device comprising an'element to be heated, anelongated heating element having a metal jacket and being distributedover a surfaceof said element to be heated and a `metal shell castaround said elements and contracted to effect intimate contact with theelement to be heat- 4ed. and secure bonding of said elements.

5. The method of forming an electrically heated device employingseparately formed heated and heatingelements which comprises casting onand about both elements a metal shell andshrinking such shell on theelement to be heated to subject the latter to a compression force.

6. The method of forming an electrically heated device employingseparately formed heated and heating elements which comprises casting onand about both elements a metal shell and controlling the relativetemperature values to effect predetermined shrinkage of such shell onthe element to be heated to subject the latter to a compression force.

7. The method of forming an electrically heated device yemployingseparately formed heated and' heating elements which com-

